1. Field of the Invention
The present invention relates to a process for preparing mono-N-sulphonylated diamines by reacting diamines with sulphonyl halides in the presence of water, base and organic solvents.
2. Brief Description of the Prior Art
Mono-N-sulphonylated diamines, especially in optically active forms, have gained high industrial significance, for example, as ligands in catalysis (see, for example, Noyori et al. J. Amer. Chem. Soc. 1995, 117, 7562).
The preparation of mono-N-sulphonylated diamines is known in principle. For example, R. A. Sheldon et al., Eur. J. Org. Chem. 1999, 2315 describe their preparation from diamines using sulphonyl halides in the presence of triethylamine.
However, a disadvantage of this process is that mixtures of unsulphonated, mono-N-sulphonated and di-N-sulphonated products are formed which have to be subjected to a complicated chromatographic separation (see also EP-A 1 174 426). In the existing processes, the selectivities range from 30 to 85%, based on the desired mono-N-substituted diamine, which is unsatisfactory for industrial implementation.
There was therefore a need to provide a process which enabled the preparation of mono-N-sulphonated diamines in an efficient manner with good selectivities.